The different sources of natural gas, including conventional wells, shale rock, and coal beds. Not included are methane hydrates, or gas trapped in ice.

For natural gas, the stars are aligned for it to play a far more substantial role in the world energy mix, according to a pair of reports this week.

The Massachusetts Institute of Technology today published its report on natural gas, which it characterized as an abundant and reasonably priced resource able to act as a bridge to a low-carbon future. The International Energy Agency released its own study (PDF) Monday, where it said natural gas is poised to enter a "golden age."

The key driver for the optimism around natural gas is supply as well as societal pressure to cut greenhouse gases and transition away from dirtier fossil fuels. Although there are considerable uncertainties, MIT estimates there are about 150 years' worth of natural gas available at current consumption rates. Burning natural gas produces about half the carbon dioxide as burning coal and has much lower levels of mercury and air pollutants.

Natural gas has become a favored energy source for many politicians in the U.S. because it's cleaner than coal and is domestic. Even without laws that put a price on carbon emissions and an unknown supply, the abundance and versatility of natural gas--which can be used for electricity, heating, or transportation--means that its use will grow significantly, according to both the MIT and IEA reports.

In the U.S., the energy picture has been dramatically changed over the past few years by tapping so-called unconventional resources of natural gas locked in shale rock. Russia, the Middle East, and the U.S. contain altogether an estimated 70 percent of supply, according to MIT.

"Gas is, globally speaking, a very young industry with a very bright future ahead of it," said Anthony Meggs, the study's co-chair and visiting engineer at the MIT Energy Initiative, during a presentation today. "Shale gas is transformative for the economy of the U.S. and potentially on a global scale."

He said that it's difficult to pinpoint the actual amount of known reserves, particularly unconventional sources outside the U.S. Drilling from shale has shown to be highly variable with some wells being less productive than expected before drilling, making them uneconomic. One of the recommendations from the report is further government-funded research into understanding natural gas reserves.

Impact on renewables, nuclear Although natural gas is considerably cleaner than coal, drilling shale gas in the U.S. has been marked with growing environmental concerns over the past few years due to the practice of "fracking," where shale rock is cracked and then released by pumping fluid into wells.

The primary concerns with fracking are preventing gas from entering water aquifers with faulty well casings and treating fracking wastewater, Meggs said. MIT said that environmental concerns are "challenging but manageable." Meggs said that drilling companies should disclose the fluids and that regulations should better address environmental issues.

"It's a big threat. The industry is doing a very poor job of organizing a coherent response to a very concerted campaign, or series of campaigns," he said. "Common sense means that less environmentally sensitive oil and gas companies (of which there thousands drilling shale gas) will lose their license to operate there...and they will gradually be squeezed out."

In recent months, there have been questions, notably from a study on lifecycle emissions from Cornell University, as to whether leakage of the potent greenhouse gas methane--the main component in natural gas--during drilling means that natural gas is a bigger contributor to global warming than coal.

The study's authors today said that even with recent revisions on emission estimates from the EPA on leakage, natural gas is still substantially cleaner. The study projects significant greenhouse gas benefits by replacing older, inefficient coal power plants with more efficient gas plants.

Although natural gas is often characterized as a bridge to a low-carbon energy supply, the low prices of natural gas pose a barrier to renewable energy and nuclear for electricity generation. "The gas price is sufficiently low that it makes it very tough for nuclear or renewables to take market share," said Henry Jacoby, MIT management professor and co-chair of the study.

Even without climate policies or mandates for cleaner energy, natural gas usage will go up in the U.S., he said. Coal accounts for about 50 percent of electricity generation, compared to 23 percent from natural gas.

Substituting natural gas for coal in commercial and industrial boilers can deliver relatively quick return on investments of a few years, said Melanie Kenderdine, executive director of the MIT Energy Initiative. Buildings account for 55 percent of natural gas demand.

MIT researchers are not bullish on natural gas for vehicles, as is called for in the revised Pickens Plans for fueling long-haul trucks with natural gas. They say there isn't a fueling infrastructure, and that there is a substantial incremental cost to converting trucks, as well as a long payback period.